1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for driving the same, and more particularly, to a liquid crystal display device and a method for driving the same, which has a gate high voltage generating circuit for preventing variation of a gate high voltage.
2. Discussion of the Related Art
Owing to advantages of a low operation voltage with a low power consumption, portable, and so on, the superthin flat panel display, especially, the liquid crystal display device, has a wide and variety of applications, such as notebook computers, monitors, air crafts, space crafts, and so on.
In general, the liquid crystal display device is provided with a liquid crystal display panel having two substrates bonded together opposite to each other with a liquid crystal layer in between, a gate driver and a data driver, a timing control unit for controlling the data driver and the gate driver, and a back light unit for supplying a light to the liquid crystal display panel. The liquid crystal display device displays an image by using a difference of transmissivities of lights passed through an orientation of liquid crystal molecules artificially controlled by controlling an electric field between the two substrates of the liquid crystal display panel.
The liquid crystal display device is provided with a power supply circuit for generating a gate high voltage VGH, and a gate low voltage VGL by using power from an external system for driving the gate driver.
The power supply circuit has a gate high voltage generating circuit. The gate high voltage generating circuit generates a gate high voltage VGH for applying to a gate driver of the liquid crystal display device by using charge pumping from a power source. In this instance, a highest gate high voltage VGH permitted to input is set by a gate voltage modulating circuit.
However, in a case the gate voltage modulating circuit sets the highest gate high voltage VGH, and the power is applied for generating the gate high voltage VGH, the gate high voltage VGH varies in a blanking period to cause temporary rise of the gate high voltage VGH. The rise reaches to a value exceeding the highest gate high voltage VGH set by the gate voltage modulating circuit, and if the highest gate high voltage VGH risen thus is supplied to the gate voltage modulating circuit, the gate voltage modulating circuit is damaged. Consequently, in order to prevent damage, a limitation is imposed, in which the gate high voltage VGH is set low, substantially.